**** is the []{} (continuative form) of the adjective **** / = " ** _sharp_** ".
"sharp" ⇒ "sharply"
It is conjugated into its so that it can modify the following verb []{}[]{} = "to rip up".
One cannot say **** . I feel like I am talking about almost everyday here (along with relative clauses). Wonder how properly those are taught in Japanese-as-a-foreign-language.
Finally, []{}("poison") or any other **noun** will not fit in grammatically.